1. Field of the Invention
The present invention relates to a work vehicle.
More particularly, the present invention relates to a vehicle speed control arrangement for a work vehicle, comprising:
speed change operating means for speed-changing a stepless speed change device to change an output from the stepless speed change device;
a brake device for braking a wheel with a braking force according to an operational position of an operational pedal which is automatically returned to a stepping release position;
a pedal sensor for detecting an operational position of the operational pedal; and
controlling means for controlling an operation of the speed change operating means based on the output from the pedal sensor, thereby to change the output from the stepless speed change device to a speed according to the output from the pedal sensor in a speed change range between a set speed preset by a speed change operational tool and a zero speed.
Also, the present invention relates to a transmission switching arrangement for a work vehicle comprising:
transmission switching means having a plurality of hydraulic clutches for switching over a transmission state of a power transmission line including speed changing means;
controlling means for controlling operations of the transmission switching means and the speed changing means; and
commanding means for commanding to the controlling means a switchover of the transmission state by the transmission switching means.
2. Description of the Related Art
[1] As a vehicle speed control arrangement of the above-described type, there is known one configured such that a vehicle body is braked and stopped in response to a movement of an operational pedal beyond a boundary position which is located between a speed change braking range and a stop braking range to reach the stop braking range; and that the vehicle body is started in response to a movement thereof beyond the boundary position back to the speed change braking range (see e.g. Japanese Unexamined Patent Application Publication No. 2010-111353 (JP 2010-111353 A)).
With the arrangement described in JP 2010-111353 A, in order to maintain the braked and stopped state of the vehicle body, it is required to keep the operational pedal in the stop braking range with a large stepping force. Therefore, if reduction occurs in the stepping force to the operational pedal when e.g. another operation is effected under the braked and stopped state, there is high possibility of the operational pedal being returned to the speed change braking range beyond the boundary position. With this, there was a risk that the vehicle body may be started inadvertently.
One object of the present invention is to prevent the possibility of inadvertent start of the vehicle body due to reduction in the stepping force to the operational pedal due to execution of another operation while the vehicle body is kept braked and stopped by a stepping operation on the operational pedal.
[2] As a transmission switching arrangement of the above-described type, there is one known configured such that a forward-reverse switching device is provided as the transmission switching means, and when the controlling means receives from the commanding means a forward-reverse switching command by the forward-reverse switching device, the controlling means controls pressures of a pair of hydraulic clutches thereby to effect a forward-reverse switchover (see e.g. Japanese Unexamined Patent Application Publication No. 2009-074617 (JP 2009-074617 A).
With the arrangement described in JP 2009-074617 A, during a high speed traveling, when the operational state of the forward/reverse switching device is switched over based on an output from the commanding means for commanding a forward-reverse switchover by the forward-reverse switching device, the amount of energy absorbed by the hydraulic clutch becomes excessive, so that there is the risk of burnout damage of the hydraulic clutches.
Thus, another object of the present invention is to restrict occurrence of burnout damage of the hydraulic clutches which may be caused by a switchover of a transmission state by the transmission switching means during a high speed traveling.